The invention relates to a method for manufacturing a sealing body, particularly for a pipe joint, comprising a retaining ring of thermoplastic material, which is to be fastened on the end portion of a pipe part, and a sealing ring disposed coaxially to said retaining ring and bonded thereto, one of these elements being previously moulded, after which the other element is moulded in a mould cavity, which is partly bounded by a part of the previously moulded element.
A method of this kind is known.
According to this known method a sealing ring consisting of a head portion and a sealing sleeve is moulded in a first mould cavity bounded by a first, a second and a third mould cavity surface. The portion of the mould cavity for the sealing sleeve is mainly bounded by the first and second mould cavity surfaces and the portion of the mould cavity for the head portion is mainly bounded by the third mould cavity surface. The third mould cavity surface is than replaced by a fourth mould cavity surface and the retaining ring is moulded by injection moulding of the thermoplastic material around the head portion of the sealing ring in a mould cavity bounded by said head portion and the fourth mould cavity surface, the sealing sleeve being confined between the first and second mould surfaces.
This method has a number of drawbacks. The retaining ring must in fact be moulded around the head portion of the sealing ring, which is often made of relatively soft material, so that on the injection of the material of the retaining ring this head portion may be deformed. In addition, the moulded sealing body is difficult to remove from the mould cavity. Moreover, the cycle time for the moulding of the sealing body is relatively long.